High temperature superconductors (HTS) are ceramic materials that exhibit zero resistance when cooled to below their superconducting transition temperature. Using superconductors for power distribution allows for significantly higher power density than legacy copper or aluminum wires. However HTS materials have to be maintained at operating temperatures, typically 30 to 80K (−243 to −193 C) in order to function properly. If a superconductor exceeds its designed temperature, it will not be able to carry the rated current and will quickly revert to or act as a normal conductor. When this happens, the superconductor effectively becomes a resistor and will transmit only the amount of current that can be sustained in its very thin metal stabilizer.
As outlined above, for proper operation of the HTS, cooling is required. Typically, a cryogen is circulated along the HTS power cables to provide the cooling. A cooling station is also used to maintain the cryogen at the desired temperature to provide the necessary cooling. HTS power cables typically use liquid nitrogen as the cryogen due to its availability, large thermal mass, ease of pumping, and dielectric properties. For Navy systems, using a liquid cryogen presents potential dangers of asphyxiation in the event of a system breach. Additionally LN2 has a lower temperature limit of 64K before it solidifies. For these reasons as well as the ability to achieve much colder temperatures, the Navy has been using gaseous helium as the cryogen for the majority of its HTS machines and systems and operates them around 30-50K. Since the gaseous helium isn't efficiently pumped, circulation is typically achieved through centrifugal fans. However, generally speaking, the prior art does not teach interconnected HTS power cables with multiple cooling stations forming a network, having the ability to reconfigure the circulation in the event that a cryogenic cooling station and/or a power cable is not functioning properly.